Thread: autolite 103's or 104

You can thank Overkill for this:

Well its super boring here at school so I thought I'd do a writeup for fun, maybe intigue some, get some ideas and get some feedback. I'm trying to do a lot of writeups for my website, so feedback, corrections and additions are greatly welcomed.

-----------------------------------------------
Spark plugs!!! We all got em, and we all go nuts figuring out what to use and why. So I wanna talk about what I use, why, and throw in a few tips I've found out about along the way.

Platinum, people here that word and think BAM these are premium plugs. What makes platinum so special? Well the answer is in the design of a platinum plug. So lets start there.

A spark plug's task is to transfer electrical current or "spark" between a power and a ground electrode to ignite the air and fuel mixture. We want this spark to be hot, to promote a nice clean burn of the mixture, as this will promote the best efficiency and therefore the most power. Now imagine two spheres electrically charged, hold them closely together and you'll see spark jump across it. Now try and separate them and you'll see the spark disappear. NOW try this with two sharp pointed electrical rods and you'll see you can hold them further apart and the spark will still jump between them. What does this mean? Sharp points will transfer the spark the most effectively. Ever notice the tip of the spark plug and how most platinum plugs are sharp tipped center electrodes? ok moving on

Sharp tips are all well and fine, but thats a hot environment down there. Infact the biggest problem is withstanding the heat. A sharp center electrode will get very hot, this promotes easy ignition (less charge to spark the plug) and a clean running plug free of deposits, but try this with a standard copper plug and it'll melt! Platinum has a much higher melting point than copper which is used on the classic style spark plug, thus the tip can be sharpened like it is. Iridium is the new guy on the block; same thing, it has an even higher melting point, thus the tip can be sharp. Now a copper plug needs to have a wide body to disperse the heat over a larger area so its tip can run cooler. Now did that set off any light bulb on where that would be beneficial? More on that in a sec...

Now colder range spark plugs. Heat ranges on a spark plug are ranges of temperatures where a plug is designed to run in its normal operation. This operating temperature is varied by the amount of the center body exposed in the plug; think of it as a mountain and the center electrode as its peak, the higher the mountain the hotter the plug. As heat builds in the cylinder to a point at which preignition occurs, it is beneficial to run a colder operating plug to cool the temperature in the cylinder overall. This prevents the preignition, saving your pistons, and also restores power lost by backed off timing advance used to counter ignition problems. This is traditionally a tuning method of those with forced induction and nitrous oxide, though when used in mild terms can be beneficial to highly modded from factory N/A motors.

Now lets deal with GTPs and GTs. A lot of GT guys get caught up with running colder plugs, cause of all the discussions by GTP guys on running colder plugs, and I'm worried that they're being misguided. As stated, running colder plugs are mostly a tuning aid to forced induction, most guys with N/A motors dont get to share in the fun

GT OWNERS, you may skip to here if technicals above bore you

For GT guys, if I was a GT owner, my battle plan would be something as follows. I would try and use a platinum, due to the hot running tip and ease of ignition. I would step down one heat range and probably try a TR55 NGK G-Power cause it has a very sharp tip. AC Delcos have a less sharp tip, so I would run 1 range cooler at MOST but try a stock heat range first in that brand. From there I would run at LEAST a .060" gap. With the ease of firing of a platinum plug and our strong DIS ignitions, you should easily be able to run this large a gap. For tweaking, I would try and open up the gap, say try .065". The more spark exposed the better, and for regular engines this is greatly more easily accomplished than FI. Little should be gained from running a colder plug for the most part, since you want a hot spark for your engines. If you are getting KR in your car, then a cold plug is a bandaid fix, you should not be getting KR troubles with a N/A car, no more than 2-3 at the most under hard acceleration. If you are getting KR, are you running a clean gasoline? Are you running high octane gas? Is your motor internally clean, free of large carbon buildup? Are you having fuel problems? Is your car running very hot in the summertime? For a GT, I would be running Sunoco 94 all the time, its highest octane and its the cleanest gas. Carbon buildup I'd make sure is minimized with throttle body cleaners and injector cleaners, maybe even a top end cleaner thats poured in. I'd run a 180 thermostat to make my engine run a tad cooler but not bone cold. And from there I would increase timing advance via a MAFT+ or a DHP computer (customized if the standard DHP is conservative). Having a hot spark, warm and not hot clean motor, with clean high octane gas and spark advance better than factory, I imagine a very responsive engine. This formula worked extremely well with my old LT1!

GTP OWNERS, you may skip to here if technicals above bore you

For GTP guys, we face a different battle We must prevent our cylinders from getting too hot. We run an inefficient blower without means of cooling the incoming charge, once we increase our boost we encounter KR due to this, plugs are a very effective tuning method! I run copper plugs. Reason being is simply that they run cool compared to platinum. AC Delco seem to have a less sharp tip than most platinums, thus the sharp tip doesn't seem to affect things as much as NGKs, anyone trying the G-Powers or Iridium NGKs though including myself, Ian Thomas, and EdZed with his Daytona edition have been less than impressed. I also run colder heat range plugs. From the factory, the minimal boost didn't seem to warrant the need for colder plugs; however once the boost is stepped up the problem becomes all too apparent. As a baseline for people:
stock boost levels - run stock heat range to 1 range colder
9-10 psi boost - run 1 full range colder (3.4 with exhaust mods)
10-11 - run 1-2 ranges colder (3.4 with no exhaust mods)
11-12 run 2 full ranges colder (3.25 with exhaust mods)
12+ - run 2-3 ranges colder. (3.25 or smaller when applicable)
Start from there, your actual needs will vary and I recommend basing them on KR levels in your specifical application. If you run 1 range colder with a 3.4 and see 3-4 KR, dont be afraid to try 2 ranges colder; in most applications this will cause no bad side effects or problems and should drop your KR 1-2 degrees. If you run a 3.25 and see greater than 4 KR, you definitely need colder plugs. If you run 1 range, step down to 2. If you run 2 ranges, step down to 3. As long as the plug is firing, its cleaning itself, so I believe if you gap right you will be able to run 2 and 3 range colder plugs in applications where its needed. For more on gapping, see below.

Now for a few tips and recommendations based on personal experience, customizing your spark plugs may be weird but give it a read

* AC Delco plugs seem to be the only platinum plugs that GTP engines respond well to. I'd recommend 41-932s (1 range colder) in this brand to those with 3.4s and minimal KR and 41-919s (2 ranges) to 3.25 users. Platinum plugs will last longer than copper and it is very understandable to want to run them compared to changing copper plugs once a year. I would also recommend, no matter the application, a .060" gap due to platinums hotter running. If you have problems, tailor the gap to your application, but I'd say start from there.
As Wilfried discovered, AC Delcos are best bought at Walmart for $12ish a pair, this is half the price of Canadian Tire. 932s are readily available at Walmart, a cheap source for 919s is still being researched.

* NGK G-Powers I would recommend to most GT owners. Try the TR55s in this plug and run a full 0.060 gap. For people like Rich Ramos with a few mods and upcoming DHP, it'd be interesting try a .065 gap to see if there's more power to be had. If anyone does try this, let me know how its performing for you, I'd be very interested in feedback.

* For copper plugs, NGK makes a TR5 which works well and is cheap and available at Canadian Tire. TR6 is available only from specialty places it seems, I got mine from Straight Line Racing. For a GTP owner with a 3.4 wanting a cooler copper plug, I'd recommend a TR5 plug. Please not
TR55 - 1/2 range colder
TR5 - 1 full range colder
So get the TR5!

For 2 and 3 heat ranges colder, plugs must be found outside of Walmart and CT, sucks I know but here's my thoughts. My experience with TR6 has been marginal. They seem to perform well at first but then lose their spunk. It may be all in my head but thats how it feels.
For 2 ranges colder, I recommend Autolite 104s. I've used these and been very happy, as have test mules Peter C and Alex P
For 3 ranges colder, I would recommend Autolite 103s. I will be trying them this year, but for 3.25 and smaller users on clubgp that I've talked to, these plugs apparently perform excellent.
Autolites are available from UAP/NAPA and should cost $3/plug.

I recommend changing copper plugs every year. The copper breaks down quicker than platinum and loses its performance. If you're good at changing plugs and run a 3.25, try running Autolites in the summer, then change to TR5s in the winter, then back to Autolites in the next summer etc, this keeps a very fresh set of plugs in your car and performance is rewarded appropriately.

Copper plugs are harder to ignite than platinum due to a less sharpened design. Due to this, I recommend decreasing the gap slightly to somewhere between .050-.058, try .055 for starters on most though the colder the heat range the more important a small gap becomes to keep the plug easy to fire. If this seems small, try going and asking a performance engine shop about running this cold a plug with that large a gap and they'll think you're crazy; our powerful ignition systems allow us to still use a near stock gap however most V8s are limited to much smaller, Straight Line recommends a .030" gap and NGK themselves recommend no bigger than .050" on their TR6s due to the weak factory ignition systems of yesteryear.

NOTE that above I said that copper plugs melt at lower temperatures than platinum. On a properly running GTP engine, without excessive preignition, this is NOT a concern whatsoever and should not be a deciding factor in your plug selection.

* Ground electrodes also play pivital roles in the plug's operation yet are usually left untouched. Here's a few very special tricks that I have picked up over the years that I shall share with you.

- When you gap the plug, you are bending the electrode. It is important to have a very parallel electrode to the bottom of the plug threads, this promotes the spark to jump to the tip of the electrode upwards rather than to the side if the electrode is bent on an angle. To do this, bend the side of the electrode straight up and then bend the top half of it over the center electrode. As the gap gets larger, the more you need to bend just the top over. This is easily accomplished using a proper plug gapper, a decent one is available at Canadian Tire, it will have the hooks on it.

- Although you want the spark to travel upward to the tip, you wish it to be as exposed as much as possible. To do this, try this:
On a sharp tipped platinum plug, bend the electrode so that its tip is over the center electrode but sticks no farther.
On a wide tipped copper plug, bend the electrode so that its tip is 1/3 to 1/2 of the way over the center electrode.
On a small gapped plug, to accomplish this may require shortening the ground electrode. To do this, use a rough file to grind it down making sure you don't damage the center electrode.
This will expose more of the spark to the open cylinder rather than having to travel around the ground electrode.

-I need to test this one more BUT I wanted to share it with GTP guys. I picked this tip up from the Mustang crowd a few years ago and its worked well so far. Mustang guys are big on Accel spark plugs to cut down on their detonation, cause of their U shaped electrode.

On the ground electrode, the part that gets the hottest is the two sharp tips at the sides on the very end. These little hot spots can cause preignition troubles in extreme cases. Rather than buying Accel plugs though, what I've been doing is ground down the sharp edges to that the tip resembles a smooth U shape. Again this is done with a rough file making sure not to damage the center body electrode.

Disclaimer: This information is to be used as reference only. Its author is not responsible for any negative effects that may occur as a result of using the methods provided in this guide. He is however hopeful that it has been helpful.
---------------------------------------------------

So there's a writeup of all my knowledge of spark plugs that have come to mind in the past two hours as I've sat here in bordom in Computer's class. Additions, corrections, thoughts, please post and let me know so it can be tweaked for my website I think its time for lunch lol